1. Field
The present disclosure relates generally to optical devices and instrumentation for ophthalmological examination.
2. General Background
Detailed images of internal structures of the retina allow detection of ocular pathology at an earlier, more treatable stage. Examinations to obtain such images are often not performed because the pupil naturally restricts the field of view, thereby limiting in turn the eye regions and structural detail apparent to the physician. Dilation of the pupil allows more light into the eye from either the ambient environment or an external light source, and also allows more light to be reflected from the eye through the enlarged aperture of the pupil.
Attempts to address this problem have taken several forms, many of which are cited in U.S. Pat. No. 7,311,401, which is hereby incorporated by reference in its entirety. Mydriasis, the drug-induced dilation of the pupil, allows sufficient light into the eye to permit detailed colored imaging of the retina, but necessitates extra time to induce dilation, and furthermore makes the patient's eyes painfully sensitive to light for hours afterward.
An alternative way of getting enough light into the eye is to use flashlamps, which emit high-intensity light. Flashlamps, however, cause patients discomfort, and according to recent studies, can damage retinal cells. In addition, flashlamp-based cameras are not amenable to extended observation, but are essentially “one shot” devices as pupil contraction occurs immediately following the flash, obviating further study.
A third approach is to use image intensifiers to make more efficient use of pupil-limited light fluxes. Image intensifiers, however, result in relatively low resolution monochrome images, thereby making detection of pathology difficult.
Thus a need exists for a way to obtain detailed, high-resolution color images of a patient's retina without use of mydriasis or light sources apart from ambient room light.